Radio receiver circuit arrangement



Oct. 26, 1948. J. VAN DER HEEM 2,452,340

RADIO RECEIVER CIRCUIT ARRANGEMENT Filed Jan. 20, 1943 "mun- HM=NW gas 230' but) Patented Oct. 26, 1948 name uucmvualcmourr ARRANGEMENT Jan van def. HelemQThe Hague, Netherlands; as-

signor to Hartford National Bank and Trust Company,;-Hartford, Conn-., as trustee Application January 20, 1943, Serial No. 473,026 In the Netherlands January 29, 1941 Section LPublic'Law 690, August 8, 1946 Patent expires January 1961 4 Claims. (01. 250-20) a :This invention relates to a radio-receiving set in which the electrode system used for detection together with an amplifying electrode system is arranged about a common cathode in one vacuum tube. Such combined electron discharge tubes :areoften used in modern radio-receiving technique. ,Thus,for-instance, low frequency output amplifying tubes incorporating'a diode are commonly known. 3 c 1 The, use of the said combined tubesin circuit arrangements inwhich-the negative grid voltage {orthe amplifying part and the retardingvoltage for automatic, volume control are obtained by meansof ,a resistance in the cathode-lead brings about. certain difficulties when the direct voltage produced upon detection in the detector circuit, is used as a control voltage for automatic volume control of the highor intermediate-frequency amplifying tube preceding the diode. Difficulties also arise if the low-frequency signal produced upon detection in the detector circuit is not directly supplied tothe control grid of the amplifying electrode system which has its cathode in commen with the detector, but is first amplified in another tube. cathode leads of the various tubes are connected each individually to the negative or earthlead ot-the set, these difficulties consist inthat in the first-mentioned case an undesirable relaxation oscillation is produced and in the second case self-oscillation of the low-frequency :ampli-fying system occurs.

According to the invention these difiiculties are overcome by connecting the cathode lead of the high-frequency or intermediate frequency tube preceding the detector and the cathode lead of the succeeding amplifying tube which amplifying tube may be interposed if required, between the detector and the amplifying tube combined therewithydirectly tothe cathode of the detector tube. The invention will be more fully explained'by reference to the accompanying drawing representing the diagram of one embodiment of the invention, from which the parts which do not appear to be of any material pertinence to .the invention have been omitted. The embodiment c'oncerns a superheterodyne receiver, but it will be appreciated that the invention is not limited to receiving sets of this type and that it also applies to any other receiver type.

Through the intermediate-frequency transformer l, 2 the intermediate-frequency voltages are supplied to the control grid of the intermediate-frequency amplifying tube 4. The amplified signals appearing in the anode circuit of In the usual circuits, wherein the I this tube are supplied through the intermediatefrequency transformer 9; ID to the detector; diode 55] of the duo-diode-pentode l7. The'lowr-frequency alternating voltage set up across the resistance 13 is entirely or partly supplied-through the condenser M to the amplifying grid 5| of the cathode-ray indicator tube l9 whichis constructed in such manner that the-control grid. 5:! of the voltage amplifying .partis electrically insulated from the control grid 52 of the indicator part. The low-frequency alternating voltage set up at the amplifying-anode 53 of thetube wand evolved across the anode resistance 26 is supplied through the condenser 18 and the lealgage resistance 20 to the control grid 54 of the tube IT. The anode circuit of the tube i'l comprises the output transformer 24, 25.

The use of the circuit referred to above involves a few difficulties which the. invention purports to avoid.

The cathode lead 55 of tube :H includes resistances 21, 28 which are bridged by the condenser 29. The negative voltage for the control grid 54 of 'tubell is takenfrom the junction of resistances 21 and 28. The voltage across .the resistances 2i and 28 is the retarding (delay) voltage for automatic volume control; to such-end the automatic volume control voltage is produced across. resistance 39 by the second diode; 56 incorporated in tube H and fed through the condenser it. The voltage so derived, is supplied throughthe resistance 3| which is by-passed by condenser 32, to the tubes to be controlled.

It is found that a relaxation phenomenon appears when the direct voltage produced by the detector diode across the resistance l3, issuppliedthroughthe resistance 12 as a control voltage, to the control-grid of :the intermediatefrequency amplifying tube 4 and when the cathode of the tube t is connected to the earth lead either directly or in the usual way through the resistance 7 for obtaining the negativegrid voltage. In fact, the alternating voltage still available across the combination of resistances ZLand 28 and condenser 2-9 is then supplied through the resistance 12 to the-control grid of thetube 4 and; will modulatejthe intermediatethe resistance 1, and the, condenser 8 serves to by-pass the screen-grid voltage of tube 4.

Another difiiculty arises when interposlng a low-frequency amplifyingtube, for instance in form of the amplifying part of tube IS in the embodiment referred to above, between the detector diode 50 and the amplifyingpart of tube l1. lIf the cathode 60 of such an amplifying tube is connected to the earth lead (through a resistance for the negative grid bias voltage; for T example through a resistance 23 lay-passed by the condenser 22) the low-frequency alternat-' ing voltage developed across the combination 21, h

28, 29 will be supplied in the correct phase for obtaining damping reductionto the control grid 5| of the amplifying tube (amplifying part of tube 19), so that the "low-frequency amplifying part of the set breaks into oscillation.

According tothe invention this can be avoided by connecting the cathode of the amplifying tube (through the resistance for obtaining the negative grid bias voltage) also to the cathode 55 of the detector diode. This is shown in the drawing'wherein the cathode 6010f tube 19 is connected to the cathode 55 by means of a conductor 6 I.

What I claim is: 1

l. A radio receiver circuit arrangement comprising an electron-dischargetube having a control grid, three anodes and a cathode common to the'control grid and the anodes to provide signal detection diode elements, automatic volume control diode elements and amplifier elements, a detector load resistance coupled to the said signal detection diode elements, a-volume control load resistance coupled to the anode of the automatic volume control diode elements and to earth, a cathode resistance interconnectingthe said cathode and earth and providing a negative grid voltage for the said control grid and'a retardin voltage for automatic volume controlyand an amplifier tube having a control grid coupled to the detector load resistance and a'cathode connected to the junction of said cathode resistance andythe said common cathode.

2. A radio receiver circuit arrangement comprising an electron-discharge tube having a control grid, three anodes and a cathode common to the control grid and the anodes to provide signal detection diode elements, automatic volume control diode elements; and amplifier elements, a detector load resistance coupled to the said signal detection diode elements, a volume control load resistance coupled to the automatic volume control'diode'elements and to earth, a cathode resistance interconnecting the said cathode and'earth and providing a negative grid voltage for the said control grid and a retarding voltage for automatic volume control, and a radiofrequency amplifier tube having an anode'coupled to the said signal detection and volume control diode elements, a control grid coupled to the detector load resistance, and a cathode connected to the junction point of said cathode resistance and the said common cathode. Y

3. A radio receiver circuit arrangement comprising an electron-discharge tube having a control grid, three anodes and a cathode common to the control grid and the anodes to provide signal detection diode elements, automatic volume control diode elements and amplifier elements, a detector load'resistance coupled to the said signal detection diode elements, a volume control load resistance coupled to the anode of the automatic volume control diode elements and to earth,

a cathode resistance interconnecting the said cathode and earth and providing a negative grid voltage for the said control grid and a retarding voltage for automatic volume control, and an audio frequency amplifier tube having an anode coupled to the said control'grid, a control grid coupled to the detector load resistance and a cathode connected to the junction point of said cathode resistance and the said common cathode.

4. A radio receiving circuit arrangement comprising an electron discharge tube having a control grid, three anodes and a cathode common to the control grid and the anodes to provide signal detection diode elements, automatic volume control diode elements and amplifier elements, a detector load resistance coupled to the said signal detection diode elements, a volume control load resistance coupled to the anode of the automatic volume control diode elements and to earth, a cathode resistance interconnectin the cathode and earth and providing a negative grid voltage for said controlgrid and a retarding voltage for automatic volume control, a radiofrequency amplifier tube having an anode coupled to the anodes of the said signal detection and volume control diode elements, a control grid and a cathode, a resistance interconnecting the control grid of the radio frequency amplifier tube and a negative potential point of the detector load resistance, and an audio frequency amplifier tube having a control grid coupled to the detector load resistance, an anode coupled to the control grid of the first discharge tube and a cathode, the cathodes of said amplifier tubes being connected to the junction of the said cathode resistance and the said common cathode. I

JAN VAN DER I'IEEM.

- REFERENCES 'CITED' The following references are of record in the file of this patent:

' UNITED STATES ATENTS Number Name Date 1,968,259 Posthumus, et a1. July 31, 1934 1,910,500 Roberts May 23,1933 2,135,560 Carlson Nov. 8, 1938 2,200,498 Haantjes et a1. May 14, 1940 c v FOREIGN PA'IENTS Number Country Date 56,587 Netherlands June 15, 1944 

